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Vessels Small Arteries

In an earlier chapter we called attention to the large inborn anatomical differences in the size and pattern of blood vessels which carry blood from the heart to the brain. This could be an important predisposing factor in senile dementia since a mild arteriosclerosis involving small arteries could be more than the equivalent of a severe arteriosclerosis when the arteries are relatively large. [Pg.256]

The mechanical force most relevant to platelet-mediated thrombosis is shear stress. The normal time-averaged levels of venous and arterial shear stresses range between 1-5 dyn/cm2 and 6 10 dyn/cm2, respectively. However, fluid shear stress may reach levels well over 200 dyn/cm2 in small arteries and arterioles partially obstructed by atherosclerosis or vascular spasm. The cone-and-plate viscometer and parallel-plate flow chamber are two of the most common devices used to simulate fluid mechanical shearing stress conditions in blood vessels. [Pg.275]

Untraumatized, freshly excised vessels are placed in cold HBSS and processed in the next few hours. Small arteries branching out from aorta have to be closed by clamping or suturing. Umbilical cord ends that have been in contact with clamps have to be cut away to ensure sterility. The vessel is flushed with PBS (100-200 ml use blunt needles to cannulate umbilical vein) until no traces of blood are visible, then its lower end is clamped and the vessel is filled with collagenase (0.5-1.0 mg/ml) in PBS prewarmed at 37°C. The upper end is then clamped, and the vessel segment is incubated for 15 min at 37° C or 40 min at room temperature. After incubation, the vessel content is poured out and the vessel is refilled a few times with 50% of its volume capacity with complete culture medium, clamped again at both ends, and agitated back and forth several... [Pg.36]

In most blood vessels, the presence of more than one AR subtype can be detected. However, a1A-ARs are widely believed to be the main subtype involved in activation of resistance artery smooth muscle (for review, see ref. 38). The small arteries of rat skeletal muscle exhibit mainly an a1A-AR profile (39) and express large quantities of intracellular receptor, as identified by the binding of BODIPY FL-prazosin (40 Fig. 5). [Pg.163]

P. Parsons-Wingerter, K.E. Elliott, J.I. Clark, and A.G. Farr, Fibroblast growth factor-2 selectively stimulates angiogenesis of small vessels in arterial tree, Arterioscler Thromb Vase Biol 20,1250-1256 (2000). [Pg.162]

CADASIL affects small arteries. It is a rare disorder resulting from Notch3 gene mutations (chromosome 19). Characteristic vascular changes can be identified in brain, skin, and muscle biopsy specimens. By light microscopy, the affected vessels have a thickened appearance, and basophilic granular material is seen by H E stain. This material is PAS positive. It displaces... [Pg.830]

NPY receptors exist in many central and peripheral tissues crucial for cardiovascular control. Peripheral NPY receptor-types have been identified by various methods. Radioligand binding has demonstrated Y1 receptors in pig renal artery and dog spleen (Lundberg and Modin, 1995), while Y2 receptors have been identified in pig spleen (Lundberg and Modin, 1995) and rabbit kidney (Sheikh etal., 1989). In blood vessels of human kidney, Y1 receptor mRNA has been detected with in situ hybridization (Wharton et al., 1993). Mainly Y1 receptors have been demonstrated in cultured vascular smooth muscle cells from porcine and rat arteries and veins (Mihara et al., 1990 Shigeri et al., 1991 Grundemar et al., 1992). Autoradiographic studies have labelled mainly Y1 receptors in small arteries in, for example, rabbit kidney (Leys et al., 1987) and rat pancreas (Sheikh et al., 1991), and intracardiac arterioles (Allen et al., 1993). On the other hand Y3-like receptors may be present in rat heart (Balasubramaniam et al., 1990). [Pg.43]

The molecular structure of the smooth muscle Kjr channel is unknown, although, based on its properties, it is likely to be a member of the IRK family. Inward rectifier potassium currents have been identified in small cerebral, coronary (see Fig. 2A), and mesenteric arterioles (<200 i.m diameter). The presence of K[r channels may be a common feature in small arteries that determine in large part peripheral vascular resistance. It is not known if Kjr channels are exclusively present in small arteries, although they have not yet been reported in larger vessels. Innervation of this size artery (<100-200 j.m) is usually sparse and therefore small arteries may be more prone to respond to metabolic demand from the tissue, as reflected by potassium efflux. Thus, the appearance of K,r channels may reflect a transition of blood flow regulation to local (tissue) control. This is an intriguing hypothesis that remains to be tested. It will be important to study systematically the distribution of the K r channel within a vascular bed, as this may have physiological consequences. Kir channels, like K and K jp channels. [Pg.217]

This chapter discusses two different tyjDes of dru whose primary purpose is to increase blood supply to an area by dilating blood vessels the antianginal and IDeripheral vasodilating drugs. Vasodilating dni relax die smoodi muscle layer of arterial blood vessels, which results in vasodilatation, an increase in die size of blood vessels, primarily small arteries and arterioles. Because peripheral, cerebral, or coronary artery disease usually results in decreased blood flow to an area, dni diat dilate narrowed arterial blood vessels will carry more blood, followed by an increase in blood flow to the affected area Increasing die blood flow to an area may r ult in complete or partial relief of symptoms. [Pg.380]

The classical view of blood flow control involved the action of vasomotor influences on a set of vessels called the resistance vessels, generally arterioles and small arteries smaller than about 100 to 150 )u.m in diameter, which controlled flow to and within an organ [56]. The notion of precapillary sphincters that control flow in individual capillaries has been abandoned in favor of the current notion that the terminal arterioles control the flow in small capfllary networks that branch off of these arterioles. In recent years, it has become clear that the resistance to blood flow is distributed over a wider range of vessel branching orders with diameters up to 500 /um. There are mechanisms to be discussed in Section 59.4.2 that are available for coordinating the actions of local control processes over wider regions. [Pg.1012]

Equations 16 and 23 [or (1.15) and (1.22)] can be used to simulate either a segment of a blood vessel or the entire blood vessel itself. In small blood vessels, the inductance L is very low compared to the resistance term R, and therefore the inductance term can be neglected in small arteries, arterioles, and capillaries. Since there is no oscillation of pressure in the capillaries, the inductance term can be neglected in vessels downstream of the capillary (i.e., venules, veins, and vena cava, etc.). [Pg.32]

In small arteries, the viscosity depends upon vessel radius and shear rate. [Pg.78]


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See also in sourсe #XX -- [ Pg.123 , Pg.934 ]




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